The present invention relates to the acquisition of threedimensional data representing measurements, dimensions, gauges, etc. of large scale objects such as free cast forging pieces or the like, with emphasis on high accuracy and precision as far as the measuring results and acquired dimensional data are concerned.
Several methods are known for measuring and gauging the dimensions of large workpieces. The most simple method are nonautomated methods using, e.g. ribbons, rulers, compasses or the like. Clearly, there is a disadvantage in this approach in that it is to a considerable extent subjective and, thus, inaccurate. Also, the data acquired in this fashion are to a very limited extent only suitable for manually inputting into a computer. In some instances, particularly where the object or parts thereof are not really accessible to a person, the approach is outright unsuitable. Examples here are high temperature objects which should not be cooled down at that point when information or its dimensions are needed.
Another method for measuring and gauging large scale objects is a geodesic method which, in modern practice, employs two theodolites. In this instance, the angular positions of the theodolites are acquired after the bearings of a particular point has been taken through these two theodolites. Data processing by means of a computer system is possible in this instance, but manual follow-up of positioning by means of sighting through the eyes is complicated, time consuming, and also not necessarily reliable.
Another method is known for contactless acquiring of the dimensions of objects using one or two dimensional operating stationary camera sensors with either video pick-up tubes of semiconductors. Here then, one has to know the distance from and angular relation to the measuring object. Owing to the limited geometric resolution and non-linearity in the optical system, as well as the sensor, large objects will in fact yield poor results.